Method of texturing metal sheet



Oct. 25, 1966 R. A. CORDRAY ET AL 3,280,614

METHOD OF TEXTURING METAL SHEET Filed Aug. 9, 1965 FIG. 3.

f/r INVENTOR R.A.CORDRAY S.R.CR OKS BY 6 A ORNEY United States Patent G 3,280,614 METHOD OF TEXTURIN G METAL SHEET Richard A. Cordray, Hinkley, and Sheridan R. Crooks,

Cleveland Heights, Ohio, assiguors to Republic Steel Corporation, Cleveland, Ohio, a corporation of New Jersey Filed Aug. 9, 1963, Ser. No. 301,141 1 Claim. (Cl. 72363) This invention relates generally to metallic sheets, and more particularly, to textured metallic sheets having a surface provided with a unique intaglio design and to a method of producing said design by means of a novel rolling process. The subject of this invention represents an improvement over applicants copending applications Serial No. 108,196, filed May S, 1961, now Patent No. 3,109,331, issued November 5, 1963, and application Serial No. 301,140, filed August 9, 1963, which latter application is a divisional application of the former.

Sheet metal, especially stainless steel, is being widely used in the architectural field, particularly for use as ornamental building panels. Quite often, the entire exterior walls of large buildings are covered with such panels and one can readily appreciate that the smooth fiat surface of such panels is most unappealing to the eye if not perfectly fiat, and in the case of stainless steel, the highly reflective nature of the surface may also be very objectionable.

Accordingly, one of the objects of this invention is to provide a metallic sheet having a random intaglio textured surface provided with a dendritic design.

Another object of this invention is to provide a novel method for imparting a pleasing and unique textured surface on metallic sheets.

A further object of the invention is to provide a method for applying to metallic sheets a non-repeating design by passing between a pair of smooth surfaced rolls a pair of metallic sheets having a texturing agent therebetween.

Still another object of the invention is to provide a method for texturing metallic sheets by the use of a recoverable design-producing agent which forms a random pattern consisting of adjacent shiny and dull or matte surfaced areas Metallic sheets have been provided with decorative or textured surfaces in the past by any one of several processes which produce metallic sheets having decorative surfaces far less appealing than the present article. The prior practice has been to impart a consistent dull or matte finish to metallic sheets by either sandblasting the surface of the sheets or by passing the sheets between rolls having a textured surface thereon. The sheets of the former group are decorative only in the sense that they are provided with a dulled or roughened surface while the latter type of sheets comprise a surface design which is necessarily of a repeating nature. In using existing forms of sheets where the design is repetitive, the problem arises during installation of having to match adjacent sheets to maintain a continuity of the repeating pat tern. This is analogous to hanging wallpaper having a repeating design. In the present instance, however, the problem is eliminated due to the non-repetitive nature of the design. Often substantial savings can be realized in the number of sheets required per installation when the necessity for matching sheets forming part of a repetitive design is eliminated.

In the above referred to copending application, the method is described wherein a powder, together with random droplets of a liquid are placed between a pair of metallic sheets prior to passing the assembled sandwich between a pair of plane-surfaced rolls.

Since the development of the above method, certain advantages in texturing without liquid have become apparent and as a result, the subject method has been devised. In the present instance, a powder is placed between two metallic sheets without the inclusion of the droplets of liquid and by maintaining control over several critical conditions, a superior article is achieved without any addition of a liquid. This current dry method possesses two advantages which have proven very important, particularly in the production of the larger sheets of textured metallic panels. First, the pattern or textured design over the length of a large metallic sheet is much more uniform because there is much less likelihood of the powder being built-up during the rolling step. The term uniform as used in connection with the present invention should not be construed to mean repetitive or regular, but rather infers a consistent random configuration without any noticeable changes in the general appearance of the design. Second, the ease of carrying out this method of operation is substantially greater, for no supply of liquid need be considered and there is only a single component to be spread or distributed over the surface of the sheet being textured. Also, after the rolling step, the subsequent recovery of the dry powder is much easier and cleaner than in the previously wet powder method.

The invention will be more readily understood by reference to the accompanying drawing, in which:

FIGURE 1 is a perspective view showing the steps of carrying out the subject invention with portions of the upper sheet broken away to illustrate the condition of the metallic sheets and the texturing agent before and after passing between the pressure rolls.

FIGURE 2 is a perspective view of a textured metallic sheet produced according to the invention.

FIGURE 3 is a partial sectional view taken along the line 3-3 of FIGURE 2, and illustrates the adjacent raised and depressed areas which form the subject design.

The random textured finish is produced on the metallic sheets by forming a sandwich or composite pack consisting of a pair of metallic sheets with a filler or texturing agent comprising metallic or non-metallic powder disposed therebetween. The composite pack is then passed between a pair of smooth-surfaced rolls which causes the powder contained between the two sheets to become fluidized as compression of the entrapped air takes place during rolling. This fluidization of the powder, permits displacement of the powder and allows flow patterns to develop within the powder mass, whereby the opposed surfaces of the sheets as they are advanced through the pressure rolls are embossed or textured according to these flow patterns. The areas of the sheets which are free of any accumulation of powder due to the above described fluidization, will retain their original thickness as well as the original shiny finish of the sheet metal, while the surfaces which are caught immediately beneath and above the powder will be compressed during the rolling to produce depressed or intagli-o areas which will have a dull or matte finish. Thus, it will be seen that the inherent abrasive action of the powder not only cuts out depressed or intaglio areas in the sheets by displacing the metal therefrom, but also leaves the same areas with a dull finish. After the composite pack has passed through the pressure rolls, the sheets are separated, the powder is reclaimed from the textured surfaces and thereafter may again be used in subsequent texturing.

The air entrapped between the pair of sheets provides the novel design set forth herein due to the action of features to have a decided grain or axis substantially,

parallel to the direction of travel. Not all of the powder is displaced in an axial direction though, as some of the powder moves laterally, at an oblique angle to the axis of travel, to provide the fern-like branches formed in the design.

Referring particularly to FIGURE 1, it will be noted that the composite pack generally designated 1 comprises upper and lower metallic sheets S and S, respectively. As seen in the left-hand portion of this figure, a layer of metallic or non-metallic powder P has been spread evenly along the lower sheet S. The completed composite pack is then passed between the plane surfaced rolls R and R, whereupon the pressure applied to the fluidized powder between the compressed sheets creates the texturing design as seen in the right-hand portion of the figure. It will be understood that the texture produced according to this method will be evenly reproduced in the juxtaposed surfaces of both sheets S and S and the opposed texture patterns will be mirror images.

FIGURE 2 shows a textured metallic sheet produced according to the above described method wherein the raised shiny portions 2 will be seen to comprise fern-like or dendritic patterns extending substantially along one axis of the sheet S. Any adjacent raised shiny portions 2 are separated by intaglio or depressed areas 3 having a dull or matte surface in contrast to the shiny raised portions. The portions 2 of the sheet are not dulled or substantially reduced in thickness by the powder P, due to the fact that the powder was fluidized by compression of the air entrapped between the rolled sheets which enabled the powder over the raised areas to be carried away by the roll pressure and prevented the powder from being compressed into the surface of the sheet now comprising the raised portions.

Each of the raised shiny portions includes a plurality of branches or leaves 4 directed obliquely from the central rib or axis of the shiny portions. It will be noted that there are slight depressions or intaglio areas 5 forming valleys in the surface of the sheets between each of the leaves or branches 4, but that these depressed areas are not nearly as deep as the previously described intaglio areas 3.

Not only stainless steel, but also aluminum or mild steel among other metals can be satisfactorily textured according to the subject method. It has been found that various types of powders may be used to achieve different texturing effects.

Any one of several metallic or non-metallic powders may be utilized to produce the texturing design. The hardness of the powders used should approximate the hardness of the metal being textured and preferably the powders should be harder, but it will be understood that it is possible to texture with powders which are softer than the metal sheets, i.e., aluminum powder can be used to texture stainless steel. Some examples of powders which have been successfully used in texturing are: silica, alumina, cement, fire clay, stainless steel, iron, and nickel. Besides the hardness requirement, it is necessary that the powder have the ability to be fluidized to some degree.

For example, large particles of sand would not function in the present method, since they are difficult to fluidize and therefore do not yield a pattern at all, but only deaden the sheet surface.

The amount of roll pressure, and therefore the amount of sheet reduction used in the process of this invention has been found to affect the quality of the textured sheet.

The desired range of degree of reduction has been found to be between 2 percent and 7 percent, although greater or lesser roll pressures can be used with a resultant sacrifice in quality of design. If this range is not adhered to, then there will be inadequate depression of the metal or else the metal will be caused to pinch and deform the opposite sides of the sheets.

The speed at which the composite pack is rolled plays a large part in controlling the formation of the textured sheet. The operable range of the roll speed has been found to be between 25 feet per minute and 200 feet per minute. Rolling the sheets outside of this range has been found to produce poorly defined patterns and to cause the metal to smear.

The weight or amount of powder spread upon the sheets definitely affects the texturing. As the weight of powder per square foot is increased, the design of the pattern changes gradually until it becomes broader and heavier by comparison. It should be noted that the fundamental appearance does not change, only the general size. The critical range lies between 1 gram of powder per square foot and 50 grams per square foot. For any given circumstance, however, the acceptable range would be limited within this range, since the smaller the rolls and the shorter the sheets, the greater the permissible weight of powder. Utilizing 50 grams of powder per square foot when passing long sheets through large rolls would produce a very pronounced buckling and pinching of the metal sheets.

The permeability or surface area of the powder which is used for texturing governs the specific characteristics of the pattern to the largest degree of any of the variables. In this sense, permeability relates to that property of the powder which most affects the fluidization of the powder particles by the air which is entrapped between the sandwiched metal sheets and assists in displacing the powder during rolling to provide the ultimate fern-like pattern. A Blaine apparatus, an accepted device for determining powder permeability, may be used and indicates in seconds, the length of time required for a specific volume of air to permeate a specific volume of the powder. For example, using 1.6 grams of powder with a permeability as measured by the Blaine apparatus of 24 seconds, and with the other variables of this invention constant, a textured pattern is produced with extremely fine detail, many veins or valleys, and which may be generally characterized as small. On the other hand, a powder with a permeability measured under the same conditions but with a value of 12 seconds, gives a large pattern and the finer veins or details are missing.

Powders which have permeabilities of only a few seconds, will give only a smeared pattern and do not texture properly. It appears that there must be a considerable portion of fines, or super fines, in order to obtain a pleasing pattern and therefore the lower limit on permeability is not readily established, since clays which are essentially impermeable, will give a textured pattern when rolled as described. The pattern becomes progressively finer, however, as the fineness of the powder increases. The above two specific permeability examples are not to be considered the upper and lower-most limits, but are merely recited to illustrate the resulting characteristics of the textured pattern so produced using these values since no specific level exists at which the pattern suddenly appears or disappears. By controlling the other variables set forth herein, it has been found that a value as low as 5 seconds as measured on the Blaine apparatus will in fact be sufiicient to practice the present invention.

We claim:

The method of texturing metallic sheets capable of elongation by roll pressure which comprises; applying a substantially uniform layer of dry powder on top of a first metallic sheet, said powder having a hardness approximating the hardness of said sheet and weighing between 1-50 grams per square foot and having a permeability of at 168.51; 5 seconds as measured by the Blaine apparatus; placing a second metallic sheet over said first sheet to form a composite pack; progressively passing the composite pack between a pair of plain-surfaced pressure rolls at a speed within the range of 25-200 feet per minute and reducing said sheet between 2-7 percent during said pass; whereby, the dry powder is fluidized by compression of the air entrapped between said sheets and progressively spread out in a predominantly longitudinal direction reverse to that of the travel of the pack through the rollers to form random fern-like areas free of powder and adjacent areas in contact with the powder so that thoseopposed areas of said sheets in contact with the powder are compressed to form depressed areas in the sheets; separating the sheets which have been textured with mirror imaged patterns; and removing the dry powder.

References Cited by the Examiner UNITED STATES PATENTS 319,306 6/1885 Palmer. 1,006,600 10/1911 Speller 29183 1,572,348 2/1926 Carow 156-63 2,024,007 12/ 1935 McColloch et a1. 2,974,709 3/1963 Gretener. 3,109,331 11/1963 Cordray et al 72-363 

